Past efforts to identify areas having higher than average indoor radon concentrations by examining the statistical relationship between local mean concentrations and physical parameters such as the soil radium concentration have been hampered by the noise in local means caused by the small number of homes monitored in some or most areas, In the present paper, indoor radon data from a survey in Minnesota are analyzed in such a way as to minimize the effect of finite sample size within counties, in order to determine the true county-to-county variation of indoor radon concentrations in the state and the extent to which this variation is explained by the variation in surficial radium concentration among counties, The analysis uses hierarchical modeling, in which some parameters of interest (such as county geometric mean (GM) radon concentrations) are assumed to be drawn from a single population, for which the distributional parameters are estimated from the data. Extensions of this technique, known as a random effects regression and mixed effects regression, are used to determine the relationship between predictive variables and indoor radon concentrations; the results are used to refine the predictions of each county's radon levels, resulting in a great decrease in uncertainty. The …

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Optical loss is studied in devices with either two aligned apertures above and below the active region or with a single effective aperture above the active region. The latter exhibit slope efficiencies of up to 1 W/A.

Sandia National Laboratories is developing Fast Track as a near term demonstration of the Straight-Line nuclear material monitoring system architecture. It will implement major elements of the Straight-Line system in a realistic system setting. Fast Track will act as a test bed to gain information on monitoring stored, weapon grade nuclear material. The Pantex plant near Amarillo, Texas has agreed to participate as a demonstration site along with sites located in New Mexico and California. Information from sensors, deployed on AL-R8 nuclear material containers and throughout the storage magazine will be collected from each site, processed and disseminated to local and remote users. Initial operation of this system was slated for June 1, 1995. This paper will address the system architecture and engineering aspects of fielding this system on a compressed time schedule. Collection of data in a nuclear environment, transmission, processing and lessons learned from deployment will also be discussed.

Laser desorption mass spectroscopy (LDMS) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI) are applicable to the high molecular weight compounds in fossil fuels which resist intact ionization. LD or MALDI of coals and extracts do not show reproducible ion intensity over mass 2000. This paper describes the scope and limitations of LD and MALD in time-of-flight mass spectrometers applied to high molecular weight molecules such as proteins and polymers. Coal was also analyzed. It is concluded that the sample preparation step is perhaps the most important part in MALDI. Observed high mass ions in coal may be from contaminant proteins. Optimal matrices must be found. Finally, the mass spectrum is senstive to number average molecular weight; a low value, however, does not preclude presence of high molecular weight species.

We have discussed recent experimental results using a resonance-Raman-based LIDAR system as a remote chemical sensor. This spectroscopy has the fundamental advantage that it is based on optical fingerprints that are insensitive to environmental perturbations. By taking advantage of resonance enhancement, which 6 orders-of-magnitude, can be as large as 4 to an increased sensing range for a given chemical concentration or lower detection limit for a given stand-off distance can be realized. The success discussed above can in part be traced back to the use of new state-of-the-art technologies which, only recently, have allowed the phenomenon of resonance-enhanced Raman spectroscopy to be fully exploited as a remote chemical sensor platform. Since many chemicals have electronic transitions in the UV/IS, it is expected that many will have pronounced resonance enhancements.

Simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS) and time-of-flight velocity (TOF) spectra have been developed to study reactions that occur during the thermal decomposition of liquids and solids. The data obtained with these techniques are the identity of the reaction products and their rates of gas formation as a function of time. Over the past several years, these techniques have been applied to the study of energetic materials that are used in propellants and explosives. In this presentation, the details of the STMBMS and TOF velocity spectra techniques will be reviewed, the advantages of the techniques over more conventional thermal analysis and mass spectrometry measurements will be discussed, and the use of the techniques will be illustrated with results on the thermal decomposition of hexahydro-1,3,5-trinitro-s-triazine (RDX).

Comprehensive monitoring can provide a wealth of sensor data useful in enhancing the safety, security, and international accountability of stored nuclear material. However, care must be taken to distribute this type of data on a need to know basis to the various types of users. The following paper describes an exploratory effort on behalf of Sandia National Labs to integrate commercially available systems to securely disseminate (on a need to know basis) both classified and unclassified sensor information to a variety of users on the interact.

The operation of the Fuel Conditioning Facility (FCF) is based on the electrometallurgical processing of spent metallic reactor fuel. The pin casting operation, although only one of several operations in FCF, was the first to be on-line. As such, it has served to demonstrate the material accountancy system in many of its facets. This paper details, for the operation of the pin casting process with depleted uranium, the interaction between the mass tracking system (MTG) and some of the ancillary computer codes which generate pertinent information for operations and material accountancy. It is necessary to distinguish between two types of material balance calculations -- closeout for operations and material accountancy for safeguards. The two have much in common, for example, the mass tracking system database and the calculation of an inventory difference, but, in general, are not congruent with regard to balance period and balance spatial domain. Moreover, the objective, assessment, and reporting requirements of the calculated inventory difference are very different in the two cases.

A superfluid Stirling refrigerator cooled to 168 mK using a 4.9% {sup 3}He- {sup 4}He mixture and exhausting its waste heat at 383 mK. Cooling power versus temperature and speed is presented for 4.9%, 17%, and 36% mixtures. At the highest concentration, a dissipation mechanism of unknown origin is observed.

Recent trends towards finer pitch devices and assembly with lead free solders have resulted in increased interest in NiPd plated component leads by the electronics industry. This paper discusses the performance of NiPd fine pitch components as determined by wettability, assembly performance and solder joint reliability. Assembly evaluations were performed with a lead free solder as well as with eutectic SnPb solder. The compatibility of the NiPd component leads with different circuit board finishes (metallic and organic azole) will also be discussed.

The authors have studied the dynamics of ultrafast internal conversion processes using femtosecond time-resolved photoionization and photoelectron spectroscopy. In hexatriene, following femtosecond pulse excitation at 250 nm, they use time-delayed photoionization to observe the formation and decay of an intermediate species on the subpicosecond time scale. With time-resolved photoelectron spectroscopy, the rapid evolution of vibrational excitation in this intermediate is observed, as electronic energy is converted to vibrational energy in the molecule. The photodynamics of cis and trans isomers of hexatriene are compared and found to be surprisingly different on the 2-3 psec time scale. These results are important for understanding the fundamental photochemical processes in linear polyenes, which have served as models for the active chromophores of many biological photosystems.

Stringent emissions requirements for stationary gas turbines have produced new challenges in combustor design. In the past, very low NOx pollutant emissions have been achieved through various combustion modifications, such as steam or water injection, or post-combustion cleanup methods such as selective catalytic reduction (SCR). An emerging approach to NOx abatement is lean premix combustion. Lean premix combustion avoids the cost and operational problems associated with other NOx control methods. By premixing fuel and air at very low equivalence ratios, the high temperatures which produce NOx are avoided. The challenges of premix combustion include avoiding flashback, and ensuring adequate fuel/air premixing. In addition, the combustion must be stable. The combustor should not operate so close to extinction that a momentary upset will extinguish the flame (static stability), and the flame should not oscillate (dynamic stability). Oscillations are undesirable because the associated pressure fluctuations can shorten component lifetime. Unfortunately, experience has shown that premix fuel nozzles burning natural gas are susceptible to oscillations. Eliminating these oscillations can be a costly and time consuming part of new engine development. As part of the U.S. Department of Energy`s Advanced Turbine Systems Program, the Morgantown Energy Technology Center (METC) is investigating the issue of …

Vinyl-bridged polysilsesquioxane gels were formed through the use of sol-gel polymerization methods. Acid- and base-catalyzed samples were prepared from both the pure cis-(l) and pure trans-(2) isomers of 1, 2-bis(triethoxysilyl)ethylene. Gelation times of the two isomers were compared. The trans monomer 2 formed gels within a week while the cis monomer I failed to gel-even after several months. Gelation of 1 could be promoted by the addition of a coordinating metal such as palladium. The resulting cis- and trans- vinyl-bridged polysilsesquioxane gels were then processed either by vacuum drying to afford xerogels or by extracting with supercritical carbon dioxide to afford aerogels. These vinylbridged polysilsesquioxanes were characterized by SEM, nitrogen sorption porosimetry, solid State {sub 29}Si and {sub 13}C NMR and x-ray powder diffraction.

This paper describes recent work to improve the measurement of the stress response of materials to intense, short pulses of radiation. When Saturn fires, large prompt electrical noise pulses are induced in stress measurement circuits. The conventional wisdom has been that the shorted guard ring quartz gauge was the only configuration with acceptable prompt signal-to-noise characteristics for stress measurements in this pulsed radiation environment. However, because of abnormal signal distortion, the shorted guard ring gauge is restricted to a maximum stress of about 8 kbars. Below this level, the normal, quantified signal distortion is correctable with analytical deconvolution techniques. The shunted guard ring gauge is acceptable for Egli fidelity measurements to about 25 kbars with negligible signal distortion. Experiments were conducted on the Saturn soft x-ray source which show that higher fidelity shunted guard ring gauges can successfully measure stress with acceptable induced noise. We also found that a 50-ohm impedance matching resistor at the gauge reduced the prompt noise amplitude and improved the baseline quality of the measurement prior to shock wave arrival.

High resolution chemical ionization mass spectrometry data support the notion that the size of the stable aromatic clusters is not large in coals except the very high rank coals and inertinite macerals. The desorption chemical ionization spectra appear representative of the sample with little discrimination for molecular types such as aliphatics.

A surface micromachined pressure sensor array has been designed and fabricated. The sensors are based upon deformable, silicon nitride diaphragms with polysilicon piezoresistors. Absolute pressure is detected by virtue of reference pressure cavities underneath the diaphragms. For this type of sensor, design tradeoffs must be made among allowable diaphragm size, and desirable pressure ranges. Several fabrication issues were observed and addressed. Offset voltage, sensitivity, and nonlinearity of 100 {mu}m diameter sensors were measured.

The operation of the Fuel conditioning Facility (FCF) is based on the electrometallurgical processing of spent metallic reactor fuel. It differs significantly, therefore, from traditional PUREX process facilities in both processing technology and safeguards implications. For example, the fissile material is processed in FCF only in batches and is transferred within the facility only as solid, well-characterized items; there are no liquid steams containing fissile material within the facility, nor entering or leaving the facility. The analysis of a single batch lends itself also to an analytical relationship between the safeguards criteria, such as alarm limit, detection probability, and maximum significant amount of fissile material, and the accounting system`s performance, as it is reflected in the variance associated with the estimate of the inventory difference. This relation, together with the sensitivity of the inventory difference to the uncertainties in the measurements, allows a thorough evaluation of the power of the accounting system. The system for the accountancy of the fissile material in the FCF has two main components: a system to gather and store information during the operation of the facility, and a system to interpret this information with regard to meeting safeguards criteria. These are described and the precision …

We report for the first time, fabrication of photoconducting UV detectors made from GaN films grown by molecular beam epitaxy. Semi-instilating GaN films were grown by the method of electron cyclotron resonance microwave plasma-assisted molecular beam epitaxy (ECR-MBE). Photoconductive devices with interdigitated electrodes were fabricated and their photoconducting properties were investigated. In this paper we report on the performance of the detectors in terms of UV responsivity, gain-quantum efficiency product, spectral response and response time. We have measured responsivity of 125A/W and gain-quantum efficiency product of 600 at 254nm and 25V. The response time was measured to be on the order of 20ns for our detectors, corresponding to a bandwidth of 25Mhz. The spectral response showed a sharp long-wavelength cutoff at 365nm, and remained constant in the 200nm to 365nm range. The response of the detectors to low-energy x-rays was measured and found to be linear for x-rays with energies ranging from 60kVp to 90kVp.

A wide range of physical and chemical methods have been used to study complex, multicomponent systems in fuel chemistry (crude oil, coal), and we are still far from complete understanding. Since chemical modification and/or solvent extraction of coal result in a number of different systems, it is important to understand the products in terms of their colloidal properties as a function of the solvent type, as well as other physical conditions. This would be helpful in design of processing techniques. Another area of research where SANS can be useful is characterization of the synthetic and modified clays being developed for processing in the petroleum industry. Major limitations for performing SANS experiments are nonavailability/high cost sof certain deuterated solvents and the paucity of beam time at the neutron scattering centers. This paper reports briefly on analysis of coal and asphaltenes.

A short review of theoretical and experimental studies of superdeformation and hyperdeformation is presented. Recent results, based on calculations carried out in a four dimensional deformation space, are presented. Very extended nuclear shapes ranging in mass from A=150 to A=200 are discussed.

Researchers contend that composite repairs (or structural reinforcement doublers) offer numerous advantages over metallic patches including corrosion resistance, light weight, high strength, elimination of rivets, and time savings in installation. Their use in commercial aviation has been stifled by uncertainties surrounding their application, subsequent inspection and long-term endurance. The process of repairing or reinforcing airplane structures is time consuming and the design is dependent upon an accompanying stress and fatigue analysis. A repair that is too stiff may result in a loss of fatigue life, continued growth of the crack being repaired, and the initiation of a new flaw in the undesirable high stress field around the patch. Uncertainties in load spectrums used to design repairs exacerbates these problems as does the use of rivets to apply conventional doublers. Many of these repair or structural reinforcement difficulties can be addressed through the use of composite doublers. Primary among unknown entities are the effects of non-optimum installations and the certification of adequate inspection procedures. This paper presents on overview of a program intended to introduce composite doubler technology to the US commercial aircraft fleet. In this project, a specific composite application has been chosen on an L-1011 aircraft in order to …

The Department of Energy is conducting an ongoing investigation of the consequences of taking fuel burnup into account in the design of spent fuel transportation packages. A series of experiments, collectively called the Spent Fuel Safety Experiment (SFSX), has been devised to provide integral benchmarks for testing computer-generated predictions of spent fuel behavior. A set of experiments is planned in which sections of unirradiated fuel rods are interchanged with similar sections of spent PWR fuel rods in a critical assembly. By determining the critical size of the arrays, one can obtain benchmark data for comparison with criticality safety calculations. The SFSX provides a direct measurement of the reactivity effects of spent PWR fuel using a well-characterized, spent fuel sample. The SFSX also provides an experimental measurement of the end-effect, i.e., the reactivity effect of the variation of the burnup profile at the ends of PWR fuel rods. The design of the SFSX is optimized to yield accurate benchmark measurements of the effects of interest, well above experimental uncertainties.

Survey researchers have long been exhorted to strive for high response rates in order to maximize the likelihood that the respondents are representative of the population being surveyed. It is not surprising then, that much survey research has been directed towards examining the effects of various manipulatable factors on response rate. It is clear that attempts to reach the goal of minimizing the likelihood of nonresponse bias through testing various methods of increasing survey response rates have consumed much research and debate. The results obtained in this research have been inconsistent. Some studies have found significant differences, others have found none. The present study was designed to determine the extent to which the results of an employment survey of former graduates of a teacher preparation program would have been affected by changes in response rate.